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MECH4301 2006

Materials Selection in Mechanical Design

Lecture 1

Materials Selection:Exploring the world of materials

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MECH4301 2006 Lecture 1 basics 2/20

The evolution of materials (Ashby, 2005)

Unit 1, Frame 1.2

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The World of Engineering Materials

Composites

Sandwiches

HybridsLattices

Segmented

PE, PP, PCPS, PET, PVC

PA (Nylon)

PolymersPolyester

PhenolicEpoxy

Soda glassBorosilicate

GlassesSilica glass

Glass ceramic

IsopreneButyl rubber

ElastomersNatural rubber

SiliconesEVA

AluminaSi-carbide

CeramicsSi-nitrideZiconia

SteelsCast ironsAl-alloys

Metals, alloysCu-alloysNi-alloys

Ti-alloys

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Materials and design (Ashby, 2005)

The goal of design: To create products that perform their function effectively, safely,at acceptable cost and environmentally sound. What do we need to know to do this?More than just test data.

DATA

Test Test data

Data

capture

Statistical

analysis

Allowables

Mechanical PropertiesBulk Modulus 4.1 - 4.6 GPaCompressive Strength 55 - 60 MPaDuctility 0.06 - 0.07Elastic Limit 40 - 45 MPaEndurance Limit 24 - 27 MPaFracture Toughness 2.3 - 2.6 MPa.m1/2

Hardness 100 - 140 MPaLoss Coefficient 0.009- 0.026Modulus of Rupture 50 - 55 MPaPoisson's Ratio 0.38 - 0.42Shear Modulus 0.85 - 0.95 GPa

Tensile Strength 45 - 48 MPaYoung's Modulus 2.5 - 2.8 GPa

Successfulapplications

$

Economic , environmental and

business caseSelection of

material and process

Potentialapplications

Characterisation Selection and implementation

INFORMATION KNOWLEDGE

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Mechanical properties illustrated (Ashby, 2005)

StiffStrong

Tough

Light

Not stiff enough (need bigger E)

Not strong enough (need biggery

)

Not tough enough (need bigger Kic)

Too heavy (need lower )

All OK !

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Intro to the courses main tool:

CES Selector software package

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Structured information for ABS*

Acrylonitrile-butadiene-styrene (ABS) - (CH2-CH-C6H4)n

General PropertiesDensity 1.05 - 1.07 Mg/m^3

Price 2.1 - 2.3 US $/kg

Mechanical PropertiesYoung's Modulus 1.1 - 2.9 GPa

Elastic Limit 18 - 50 MPa

Tensile Strength 27 - 55 MPa

Elongation 6 - 8 %

Hardness - Vickers6 - 15 HV

Endurance Limit 11 - 22 MPa

Fracture Toughness 1.2 - 4.2 MPa.m1/2

Thermal PropertiesMax Service Temp 350 - 370 K

Thermal Expansion 70 - 75 10-6/K

Specific Heat 1500 - 1510 J/kg.K

Thermal Conductivity 0.17 - 0.24 W/m.K

Electrical PropertiesConductor or insulator? Good insulator

Optical PropertiesTransparent or opaque? Opaque

Corrosion and Wear Resistance

Flammability AverageFresh Water Good

Organic Solvents Average

Oxidation at 500C Very Poor

Sea Water Good

Strong Acid Good

Strong Alkalis Good

UV Good

Wear Poor

+ links to processes

*Using the CES Level 2 DB

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Unstructured information for ABS*What is it?ABS (Acrylonitrile-butadiene-styrene ) is tough, resilient, and easily molded. It isusually opaque, although some grades can now be transparent, and it can be given vivid colors.ABS-PVC alloys are tougher than standard ABS and, in self-extinguishing grades, are used for the

casings of power tools.

Design guidelines. ABS has the highest impact resistance of all polymers. It takes colorwell. Integral metallics are possible (as in GE Plastics' Magix.) ABS is UV resistant for outdoorapplication if stabilizers are added. It is hygroscopic (may need to be oven dried beforethermoforming) and can be damaged by petroleum-based machining oils.

ABS can be extruded, compression moulded or formed to sheet that is then vacuum thermo-formed. It can be joined by ultrasonic or hot-plate welding, or bonded with polyester, epoxy,isocyanate or nitrile-phenolic adhesives.

Technical notes.ABS is a terpolymer - one made by copolymerising 3 monomers: acrylonitrile, butadiene and syrene. The acrylonitrilegives thermal and chemical resistance, rubber-like butadiene gives ductility and strength, the styrene gives a glossy surface, ease of machiningand a lower cost. In ASA, the butadiene component (which gives poor UV resistance) is replaced by an acrylic ester. Without the addition ofbutyl, ABS becomes, SAN - a similar material with lower impact resistance or toughness. It is the stiffest of the thermoplastics and hasexcellent resistance to acids, alkalis, salts and many solvents.

Typical Uses. Safety helmets; camper tops; automotive instrument panels and other interior components; pipe fittings; home-securitydevices and housings for small appliances; communications equipment; business machines; plumbing hardware; automobile grilles; wheelcovers; mirror housings; refrigerator liners; luggage shells; tote trays; mower shrouds; boat hulls; large components for recreational vehicles;weather seals; glass beading; refrigerator breaker strips; conduit; pipe for drain-waste-vent (DWV) systems.

The environment. The acrylonitrile monomer is nasty stuff, almost as poisonous as cyanide. Once polymerized with styrene it becomes

harmless. ABS is FDA compliant, can be recycled, and can be incinerated to recover the energy it contains.

*Using the CES Level 2 DB

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CES : the 3 levels

Level 1 1st year students:Engineering andMaterials Science.

64 materials, 60processes

Who is it for?

Level 2 2nd - 4th yearstudents of Engineeringand Materials Science

and Design.

91 materials, 68processes

Level 3 4th year, masters andresearch students ofEngineering Materials

and Design.

Technical data for3000 materials and200 processes.

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Finding information with CES

Links

Data

tableProcessesMaterials

Data

table

Find what?

Which table?

Choose what you want toexplore (materials, processes..)

MaterialsMetals

Polymers

Ceramics

etc

ProcessesCasting

Moulding

Powder

etc

Browse Select SearchToolbar Print Search web

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Relationships, perspective and comparisons

Material bar-charts

Material property charts

Data sheets do not allow comparison,

perspective. For these we need

Metals Polymers Ceramics Hybrids

PEEK

PP

PTFE

WC

Alumina

Glass

CFRP

GFRP

Fibreboard

Young

sm

odul u

s,G

Pa

Steel

Copper

Lead

Zinc

Aluminum

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Creating charts

Property

New

Graph stage

Limit stage

Tree stage

Browse Select Search Print Search webToolbar

Property

2

Property 1

Select what? Materials, Level 1

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Bar- chart created with CES (Level1)

Bar Charts allow exploring relationships

Bar Charts allow selection and sorting

UntitledMaterials:\MET ALS Materials:\POLYMERS Materials:\CERAMICS and GLASSES Materials:\COMPOSIT ES

Young'sModulus(GPa)

1e-004

1e-003

0.01

0.1

1

10

10 0

1000

Low alloy steel

Mg-alloys

Al-alloys

Zn-alloys

Ti-alloys

Cu-alloys

Stainless steel

High carbon steel

Acetal, POM

Polyurethane

EVA

IonomerPTFE

WC

Alumina

Glass Ceramic

Silica glass

Soda-Lime glassPolyester, rigid

PC

PS

PUR

PE

ABS

PP

BC

SiCAl-SiC Com posite

CFRP

KFRP

GFRP

Plywood

Neoprene

Natural Rubber (NR)

CompositesPolymersMetals Ceramics & glass

Youngs

modulus

(G

Pa)

Metals Polymers Ceramics Hybrids

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Material property- charts: modulus - density

0.1

10

1

100

Metals

Polymers

Elastomers

Ceramics

Woods

Composites

Foams

0.01

1000

1000.1 1 10

Density (Mg/m3)

YoungsmodulusE,

(GPa

)

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Mechanical properties: modulus and density (CES chart)

Questions:

Why the enormousdifferences?

Why are metals hereand polymers here?

Bonding, packing.

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Thermal properties

Questions:

Why the enormousdifferences?

What determines expansionand conductivity?

Electronic and phonon

contributions to conductivity

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Charts offer both Methods and Tools

Materials that are stiff?

At this stage you have a selection tool.

Materials with low expansion?

Charts help developing a perspective

with high conductivity?

Materials that are light and compliant?

Materials that are light and stiff?

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4301 L 1_2006

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